In the field of integrated circuits there is a trend towards the integration in a same semiconductor chip of different kinds of devices, such as DMOS-technology power devices, bipolar power devices, and low-voltage bipolar and CMOS devices.
The known manufacturing processes of DMOS-technology power devices (vertical or lateral DMOS transistors, IGBTs) involve long thermal processes at high temperatures. In fact, the channel region of the DMOS structure is formed by means of the difference in the lateral diffusion of dopants. In order to obtain DMOS devices with threshold voltages in the range of 1-2 V and with a breakdown voltage not limited by channel punchthrough, the temperature of the diffusion process must be higher than 1000.degree. C.
On the contrary, in the field of VLSI circuits there is a trend towards a reduction of the thermal budgets of the diffusion processes: high temperature and/or long duration thermal processes are not suitable to achieve the desired reduction in the dimensions of the devices, and would increase the defectivity in the thinner oxide layers. This is particularly true for non-volatile memory devices, where oxide thicknesses lower than 80 Angstroms are typical.
Consequently, the known manufacturing processes for DMOS-technology power devices, involving such a high thermal budget, are not compatible with current manufacturing processes used in the fabrication of VLSI circuits.